The following relates to the electric power arts, energy conservation arts, electric system monitoring and maintenance arts, and related arts.
Historically, electrical power grids have operated on a demand mode, in which the power grid provides a constant voltage from which electrical loads can draw power at any time. This requires substantial grid generating capacity, which must be adjusted in real-time as load increases or decreases. To mitigate such load variation, some electrical utilities provide various incentives to encourage users to perform “load shifting” in which electrical loads are preferentially operated during off-peak hours when the aggregate load capacity is lower. However, incentivizing load shifting is a relatively slow process and cannot respond to more rapid grid fluctuations.
In so-called “demand response” approaches, some automation is provided by which electrical loads are controlled remotely to help accommodate grid fluctuations. In a typical demand response system, each electrical load has a load controller that can cycle the load on or off, and/or adjust its power draw, based on control inputs received from the power grid operator or an associated entity. In a residential setting, some appliances that are Loads most suitable for demand response operation are those which have some energy storage capacity so that the load can provide service to the end-user via the stored energy when not receiving electrical power, or conversely can receive electrical power and store it for later use. In a residential setting, some suitable demand response loads include electric water heaters which store thermal energy in the hot water tank, and electric air conditioners which can store thermal energy in the form of a cooled room. Another type of electrical load that may be suitable for demand response operation is a load whose time of running is flexible—in the residential setting, such a load is an electric dish washer that may be loaded with dishes and set up to run in the evening, but may actually run at any time overnight.
Demand response systems bias residential electrical power draw toward a schedule that accommodates the utility company. This however must be balanced against the needs/desires of the resident/user. For example, an electric water heater under demand response operation should still turn on in response to the water temperature falling below the bottom of the dead band so as to ensure the supply of hot water, and conversely should turn off in response to the water temperature rising above the top of the dead band to avoid outputting overheated or scalding-hot water. More sophisticated approaches for accommodating user interest may attempt to anticipate the user's needs—for example, the demand response system may bias against operating a water heater whose water temperature is near the top of (but still within) the dead band, and conversely may bias toward operating a water heater whose temperature is near the bottom of (but still within) the dead band.